SAN FRANCISCO -- State Assemblyman Tom Ammiano, D-San Francisco, announced Monday he has introduced legislation to legalize and tax marijuana in the state of California.

AB 390 would require that all sales of marijuana be made by licensed sellers and that sales be taxed $50 per ounce. It would also forbid sales to anyone under 21.

"With the state in the midst of an historic economic crisis, the move towards regulating and taxing marijuana is simply common sense," Ammiano said at a morning news conference at the state building on Golden Gate Avenue in San Francisco.

Ammiano said the law, if passed, could generate more than $1.3 billion in much-needed revenue for the state.

"California has the opportunity to be the first state in the nation to enact a smart, responsible public policy for the control and regulation of marijuana," he said.